Method and system for creating and implementing zones within a fibre channel system

ABSTRACT

In a system comprising a first fabric and a plurality of devices coupled to the fabric by fibre channel connections, the devices are logically grouped to form configurations and zones. A configuration includes at least one zone, and each zone includes at least one device as a member of the zone. Communications between the devices is restricted according to the configuration currently in effect. For example, one device may be permitted to communicate with another device only if they are members of a common zone.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Serial No. 60/105,423, “Zoning”, by David Banks, KumarMalavalli, Paul Ramsay, Kha Sin Teow, and Jieming Zhu, filed Oct. 23,1998, which subject matter is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to a method for creating andimplementing zones within a network communication system, and moreparticularly to a method for creating and implementing such zones fordevices within a network communication system using fibre channelconnections.

2. Description of the Related Art

As the result of continuous advances in technology, particularly in thearea of networking such as the Internet, there is an increasing demandfor communications bandwidth. For example, the transmission of data overa telephone company's trunk lines, the transmission of images or videoover the Internet, the transfer of large amounts of data as might berequired in transaction processing, or videoconferencing implementedover a public telephone network typically require the high speedtransmission of large amounts of data. As applications such as thesebecome more prevalent, the demand for communications bandwidth capacitywill only increase.

Fibre channel is a transmission medium that is well-suited to meet thisincreasing demand, and the Fibre Channel family of standards (developedby the American National Standards Institute (ANSI)) is one example of astandard which defines a high speed communications interface for thetransfer of large amounts of data via connections between a variety ofhardware devices, including devices such as personal computers,workstations, mainframes, supercomputers, and storage devices. Use offibre channel is proliferating in many applications, particularlyclient/server applications which demand high bandwidth and low latencyI/O. Examples of such applications include mass storage, medical andscientific imaging, multimedia communications, transaction processing,distributed computing and distributed database processing applications.

In one aspect of the fibre channel standard, the communications betweendevices is based on the use of a fabric. The fabric is typicallyconstructed from one or more fibre channel switches and each device (orgroup of devices, for example, in the case of loops) is coupled to thefabric. Devices coupled to the fabric are capable of communicating withevery other device coupled to the fabric.

However, there are situations where the ability to freely communicatebetween all devices on a fabric is not desirable. For example, it may bedesirable to screen off certain devices on a fabric in order to performtesting and/or maintenance activities on only those devices, withoutrisking interfering with the other devices on the fabric. Alternately,devices may be segregated according to use. For example, the devicescoupled to the fabric may be segregated in one fashion during normaloperation and in another fashion to facilitate back-ups or systemmaintenance. As another example, different levels of security may beenforced by allowing only certain sets of devices to communicate witheach other. As a final example, devices may be segregated according byoperating system or other technical features.

Conventional fibre channel fabric topologies do not allow the logicalsegregation of devices which are coupled to the same fabric. Rather,devices can be prevented from communicating with each other typicallyonly if they are actually physically separated (e.g., coupled todifferent fabrics). However, this method does not facilitate the dynamicre-configuration of connections between devices since eachre-configuration requires a physical recoupling of devices.

Thus, there is a need to configure a fabric so as to restrictcommunications between sets of devices connected to the fabric. There isfurther a need to be able to dynamically re-configure the fabric and tosupport multiple configurations of device connections.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method is for use in asystem comprising a first fabric and a plurality of devices coupled tothe first fabric by fibre channel connections. The method is forlogically organizing the devices and includes the following steps. Adefinition of a first configuration is accessed. The first configurationincludes at least one zone, and each zone includes at least one deviceas a member of the zone. Responsive to the definition of the firstconfiguration, communications between the devices coupled to the firstfabric is restricted. The first configuration may be an effective one ofa plurality of configurations. The members of each zone may beidentified in a number of ways, including by the port on the fabric towhich the member device is coupled, by a name for the device which isindependent of the device's location on the fabric, or by an arbitratedloop physical address.

In one embodiment, communications between devices are restricted asfollows. When a first device queries for the address of a second device,the address is returned only if the first and second device are membersof a common zone. This prevents the first device from learning theaddresses of other devices connected to the fabric but not within acommon zone with the first device. Alternately or additionally,communications may be restricted by blocking communications betweendevices if they are not members of a common zone. In another aspect ofthe invention, at least one zone is characterized by a type ofcommunication, such as read-only access or a specific communicationsprotocol, and communications within that zone are restricted to thespecified type of communication.

In another aspect of the invention, zoning configuration information isstored within the fabric itself and/or the zoning functionality isimplemented by the fabric. Additionally, the zoning configurationinformation and/or zoning functionality may be distributed among theindividual fabric elements which make up the fabric.

In another aspect of the invention, a fabric element includes aplurality of ports, a storage medium, and a logic device coupled to eachof the foregoing. Each port is adapted to be coupled to a device by afibre channel connection. The storage medium is for storing a definitionof the first configuration. The logic device restricts communicationsfor devices coupled to the plurality of ports, responsive to thedefinition of the first configuration.

In yet another aspect of the invention, zoning is implemented bysoftware.

Zoning is advantageous because it overcomes many of the limitations ofcompletely open connectivity between all devices coupled to the fabric.Zoning allows for the creation of segmentation or zones within a fabric.This allows the devices coupled to the fabric to be subdivided intological groups of devices without the need to physically re-configurethe network. Zones may be used to create different user groups, test andmaintenance areas, and/or security barriers between devices. Zones aredynamic and can be easily and quickly changed to suit varying networkneeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention has other advantages and features which will bemore readily apparent from the following detailed description of theinvention and the appended claims, when taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram of a fibre channel network communication system 100utilizing zoning in accordance with the present invention;

FIG. 2 is a diagram of system 100 utilizing a second example of zoning;

FIG. 3 is a flow diagram of a method of zoning in accordance with thepresent invention;

FIG. 4 is a diagram of a preferred embodiment 400 of fibre channelsystem 100 utilizing zoning;

FIG. 5 is a flow diagram of a preferred method of zoning based on theSimple Name Server (SNS); and

FIG. 6 is a flow diagram of another preferred method of zoning.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a diagram of a fibre channel network communication system 100utilizing zoning in accordance with the present invention. As usedherein, the term “fibre channel” refers to the Fibre Channel family ofstandards as well as other flexible, expandable network connectivitysystems capable of moving data over long distances and supporting avariety of protocols. The fibre channel network communication system 100comprises a fabric 110 and a plurality of devices 120, 122, and 124and/or groups of devices 130. Fabric 110 is coupled to the variousdevices 120, 122, 124, and 130, and acts as a switching network to allowthe devices to communicate with each other.

In the examples which follow, fabric 110 is a fibre channel network madeup of one or more interconnected fibre channel switches (not shown inFIG. 1), although the invention is not limited to such fabrics or tofibre channel. Devices 120, 122, 124 may be any type of device, such asa computer or a peripheral, and are coupled to the fabric 110 using apoint-to-point topology. Fabric 110 is also coupled to loop 130. Loop130 includes a hub 132 and devices 134, 136, and 138, which are coupledin a loop topology. In a preferred embodiment, the loop 130 comprises anarbitrated loop with ring connections for providing multiple nodes withthe ability to arbitrate access to a shared bandwidth.

In FIG. 1, fibre channel system 100 includes two zones 140 and 142. Zone140 contains device 120 and device 122. Zone 142 contains device 124 andloop 130. Devices within the same zone may communicate with each other.Thus, for example, devices 120 and 122 may communicate with each otherbecause they are both members of zone 140. Likewise, device 124 and loop130 may communicate with each other because they are both members ofzone 142. However, device 124 cannot communicate with device 120 becausedevice 124 and device 120 are not members of a common zone. Similarly,device 124 cannot communicate with device 122; and loop 130 cannotcommunicate with either device 120 or device 122.

Zone 140 and zone 142 may be designated to be in effect at separatetimes or at the same time. If zones 140 and 142 are in effect at thesame time, they would constitute a zone configuration 150. When a zoneconfiguration is in effect, all zones that are members of thatconfiguration are in effect.

FIG. 2 is a diagram of system 100 illustrating another exampleconfiguration 210. Configuration 210 includes zones 140 and 200. Zone140 is as defined in FIG. 1. Zone 200 includes devices 120 and 124. Adevice may be a member of more than one zone concurrently, as shown bydevice 120 which is a member of both zone 140 and zone 200. Device 120may communicate with both device 122 and device 124. However, device 122may not communicate directly with device 124, and vice versa.Furthermore, in configuration 210, loop 130 may not communicate with anyof the devices 120, 122, or 124.

Note that zone configurations 150 and 210 may be stored and recalled atvarious times, thus facilitating the implementation of zones. Forexample, configuration 150 may be the configuration which is normally ineffect because devices 120 and 122 are used by one group of people anddevice 124 and loop 130 are used by another group. Configuration 210 maybe used when loop 130 requires servicing. Note that in configuration210, loop 130 is isolated from the other devices, which would minimizeany disruption to devices 120, 122, and 124; and devices 120 and 124 arezoned together, perhaps because device 120 serves as a temporarysubstitute to loop 130.

FIG. 3 is a flow diagram of a method of zoning in accordance with thepresent invention. In step 300, a zone configuration is defined. Forexample, in FIG. 1, zone configuration 150 would be defined to includezones 140 and 142, each of which is defined to include their respectivedevices. As noted above, any zones which are in effect at the same timemake up a zone configuration. Hence, defining a zone inherently alsodefines a zone configuration (i.e., the configuration consisting of thedefined zone); so step 300 is not intended to require the explicitdefinition of a configuration. For example, in FIG. 1, supposed thatthere was only one zone: zone 140. Defining zone 140 would also definethe configuration including zone 140. In step 310, the zoningconfiguration is implemented. As described previously, implementation ofa configuration restricts communications between devices according tothe zones in the configuration.

Zoning is beneficial for a number of reasons. For example, it allows forgreater flexibility in managing a network. In one application, differentzones could be defined for different user groups with each zone set upto meet the needs of the corresponding user group. Zoning can also beused to set up barriers between different operating environments, todeploy logical fabric subsets by creating closed user groups, or tocreate test and maintenance areas that are separate from the rest of thefabric. Zoning allows the network to be subdivided for these and otherpurposes in a dynamic fashion and without the need to restructure thephysical configuration of the network. This makes logically separatingdevices from each other faster, safer and easier.

Zoning may be implemented in a variety of different ways and FIGS. 4-6illustrate two preferred embodiments for implementing zoning within afibre channel system. FIG. 4 is a diagram of a preferred embodiment 400of fibre channel system 100 utilizing zoning. FIG. 4 shows furtherdetails of the fabric 110, devices 120, 122 and 124, and loop 130.Fabric 110 is comprised of three fabric elements 420, 440 and 450,preferably Silkworm switches series 2100, 2400, or 2800 manufactured byBrocade. Each switch 420, 440 and 450 contains ports to which devicesmay be coupled. In a preferred embodiment, these ports are implementedon Application Specific Integrated Circuits (ASICs) that may be pluggedinto or removed from a switch, thus allowing modularity regarding whatports are supported by each switch. Different types of ports supportdifferent types of connections from devices to a switch. An F_Port is alabel used to identify a port of a fabric that is used to directlycouple the fabric to a single device, such as a computer or peripheral.An FL_Port is a label used to identify a port of a fabric that is usedto couple the fabric to a loop. The F_Port and the FL_Ports shall bereferenced jointly as Fx_Ports. An E_Port is a label used to identify aninter-switch expansion port used to connect to an E_Port of anotherswitch in order to build a larger switch fabric.

For this example, the relevant ports on switch 420 are F_Ports 422 and432 and E_Ports 424 and 434. Similarly, switch 440 contains an F_Port442 and E_Ports 444 and 446. Switch 450 contains an FL_Port 452 and twoE_Ports 454 and 456. Switch 420 is coupled to switch 450 via E_Ports 434and E_Port 454. Switch 450 is coupled to switch 440 via E_Port 456 andE_Port 446. Switch 440 is coupled to switch 420 via E_Port 444 andE_Port 424.

Devices coupled to the fabric are also identified as ports. An N_Port isa label used to identify a device coupled to the fabric. Device 120 iscoupled to switch 420 via N_Port 460 and F_Port 422; device 124 iscoupled to switch 420 via N_Port 470 and F_Port 432; and device 122 iscoupled to switch 440 via N_Port 480 and F_Port 442. An NL_Port is alabel used to identify a device which is coupled to the fabric using aloop topology. Devices 134, 136, and 138 are coupled to loop 130 viaNL_Ports 496, 494 and 492, respectively. Loop 130, in turn, is coupledto switch 450 via FL_Port 452. The N_Ports and the NL_Ports shall bereferenced jointly as Nx_Ports.

Each switch 420, 440 and 450 also contains an embedded centralprocessing unit (CPU) module 428, 448 and 458 which controls the switch.These CPU modules typically include some sort of processor as well aslocal memory. As part of this control, each embedded CPU module 428, 448and 458 provides support to its associated switch for operating a SimpleName Server (SNS) module. The SNS in a fabric provides addressinformation to devices about other devices connected to the fabric. Aspart of the fibre channel standard, Nx_Ports joining a fabric typicallymust register their fibre channel attributes with the SNS. Theytypically also query the SNS for address information and attributes ofother devices (e.g., other Nx-Ports) on the fabric. In response, the SNSprovides an address list of other devices on the fabric. If addressinformation changes at a later time, for example due to zoning changes,the fabric sends a change signal to each device to instruct them torequery the SNS for updated address information.

It should be understood that the examples discussed herein are purelyillustrative. For example, referring to FIG. 4, fabric 110 may becomprised of a single switch or large numbers of switches. Other E_Portconnection combinations could be used to couple the switches 420, 440,and 450 together to form fabric 110. Similarly, other number and typesof ports may be contained within each switch. The composition ofconfigurations 150 and 210 from FIGS. 1 and 2, and of the zones withinthese configurations is also merely illustrative.

FIG. 5 is a flow diagram of a preferred method of implementing zoningbased on the Simple Name Server (SNS). Additional zoning software isadded to the existing SNS addressing functions to implement zoning. Thiszoning software loads zoning configuration information in the form of adatabase into the CPU of each switch. The zoning configuration databaseis replicated and propagated to each individual fabric switch. Forexample, referring to the example of FIG. 4, each switch 420, 440 and450 would have a copy of the information defining configurations 150 and210. The SNS will use this zoning configuration information to determinewhich devices are allowed to communicate with each other under thezoning configuration in effect. Since each switch maintains its own copyof the zoning information, a single switch failure will not interruptzoning enforcement to other devices on the fabric.

In step 500, a device attached to the fabric queries the SNS regardingaddress information for other devices attached to the fabric. Thistypically occurs, for example, when a device is first coupled to thefabric in order for the device to determine what other devices areattached to the fabric. If the addressing information contained in theSNS or the zoning information changes, the SNS sends a signal to alldevices instructing them to requery 500 the SNS for updated addressinformation. In FIG. 4, when device 122 first attaches to the fabric110, device 122 may query 500 the SNS (which is implemented as softwarerunning on CPU 448) to learn what other devices are also attached tofabric 110. This information is provided as a table of addresses withwhich device 122 may communicate. If the zoning configuration for thefabric 110 changes, device 122 will receive a signal from the SNSinstructing it to re-load the address database, in which case device 122will repeat step 500.

In step 510, the SNS processes the request for information understandard SNS operating procedures. In the current example, in responseto device 122's queries, an SNS without zoning capability would identifydevices 120 and 124 and loop 130 as being attached to the fabric 110,and would return the addresses of all of these devices. Device 122 wouldthen have the addresses of these other devices and would be able tocommunicate with them.

However, an fabric with the zoning software enabled performs anadditional feature. If a zone configuration is enabled in the fabric110, the SNS does not automatically send back a list of all devicesconnected to the fabric 110. Rather, in step 520, a zone check isperformed. The zoning software uses the zoning configuration informationto determine which devices share a common zone. Each device address tobe provided to another device requesting an address update is checked toensure the two devices share a common zone. The SNS replies in step 540only with the addresses of those devices sharing a common zone with therequesting device. The addresses of devices which are not in the samezone as the requesting device are not returned as shown in step 530 and,therefore, the requesting device does not know that these other devicesexist. This effectively makes devices not within the same zone invisibleto each other, although they are still connected to the same fabric.

Continuing the current example, assume that configuration 150 is ineffect. In response to device 122's query for a list of all devicesattached to fabric 110, the SNS would reply 540 only with the identityof device 120 since it is the only device sharing a zone with device122. The addresses of device 124 and loop 130 would be eliminated duringthe zone check 520 and therefore would not be included on the list ofaddresses sent to device 122 in step 530. Hence, device 122 would notknow about device 124 or loop 130, making it more difficult for device122 to communicate with those devices. Without device 124's address,device 122 cannot send messages to device 124. On the other hand, if theSNS provides to device 122 the correct address for a destination device,device 122 may send messages via the fabric 110 to that destinationdevice.

In this embodiment, the functions performed by the SNS change dependingon whether or not zoning is implemented. However, the SNS protocolitself and the manner in which the devices query the SNS are not changedby the implementation of zoning. In other words, the various devicesquery the SNS in the same manner, regardless of whether zoning isimplemented. Zoning is implemented entirely by changing the SNS'sresponses to the queries. This is advantageous because no change isrequired in the: devices themselves or their drivers in order toimplement zoning. For example, to upgrade a fabric without zoningcapability to one with zoning capability only requires the addition ofthe zone check software. No change to the devices is required.

FIG. 6 is a flow diagram of another preferred method of zoning. In step600, a source device obtains the address of a destination device. If thetwo devices are in a common zone, then the source device should bepermitted to send a message to the destination device. Otherwise,transmission of the message should be blocked. In step 610, the sourcedevice sends a message (i.e., a frame according to the fibre channelstandard) to the fabric 110 for routing to the destination device. Instep 620, the fabric 110 performs a zone check to confirm that thesource and destination devices are in a common zone. If they are, themessage is routed 630 to its final destination. Otherwise, the messageis not routed 640. Not routing the message 640 may result in differentactions being performed depending on the type of message being sent. Forexample, when the hardware zone check detects an illegal frame, a Class3 frame is discarded, whereas a Class 2 frame is given to the switchfirmware so that a reject signal can be transmitted to the sourcedevice.

The method illustrated in FIG. 6 is preferably implemented in additionto the SNS-based method shown in FIG. 5. This provides additional zoningprotection in the event that a fabric device inadvertently obtains theaddress of a destination device not within its zone. For example, olderdevices connected to a fabric may not support the SNS function and relyinstead on permanent device address lists which may be inconsistent withthe actual fabric configuration. In such cases, it is desirable to havean additional method for enforcing zoning.

Within the fabric, the zone check may occur at any or all of a number oflocations. For example, referring again to FIG. 4, supposed that device122 desired to send a message to device 124 in violation ofconfiguration 150. The communications path might be N_Port 480 to F_Port442 to E_Port 444 to E_Port 424 to F_Port 432 to N_Port 470. The zonecheck may be performed at many different locations along this path.

In a preferred embodiment of the invention, the zone check is performedat the destination port of the fabric (F_Port 432 in the above example).The zone check preferably is not implemented by the ports on the devices(i.e., the Nx_Ports) because this would require upgrading of all devicesin order to implement zoning, as opposed to just upgrading the fabric110. Of the various locations on the fabric 110, the source port F_Port442 and destination port F_Port 432 are preferred because thecommunications path must contain these two ports. In contrast, the twoE_Ports 444 and 424 would be bypassed if the communications path was viaswitch 450.

Zone checking at the destination port is preferable because it is moreimportant to protect devices from receiving messages sent by otherdevices outside their zone than it is to prevent devices from sendingmessages to other devices outside their zone. More specifically, eachfabric switch 420, 440, 450 may or may not be zoning-enabled, dependingon whether zoning software has been installed on that switch. If aswitch is zoning-enabled, the devices connected to it are not expectingto see messages from devices outside of their zones because they expectthe switch to enforce zoning. That is, the devices are zoning-aware.However, devices connected to a switch that is not zoning-enabled haveno such expectations, i.e. they are zoning-unaware. A zoning-unawaredevice has no knowledge of zoning and is prepared to acceptcommunications from any other device in the fabric system.

When the zone check is performed by the destination port within thefabric communication pathway, a zoning-enabled switch will blockimproper transmissions from being sent to its attached zoning-awaredevice, in accordance with the device's expectations. In contrast, aswitch which is not zoning-enabled will not block impropertransmissions, but this is also in accordance with the destinationdevice's expectations since the destination device is zoning-unaware andis not expecting any screening of transmissions due to zoning.

Now consider the situation when the zone check is performed by thesource port. If the switch attached to the source device iszoning-enabled, messages will be properly filtered based upon theenabled zoning configuration. However, if the switch attached to thesource device is not zoning-enabled, messages will not be properlyfiltered. Unfortunately, in this case although the source device iszoning-unaware, the destination device may or may not be zoning-aware.Thus, a zoning-aware destination device may still receive an impropercommunication.

Referring again to FIG. 4, in a preferred embodiment, the zone check isimplemented by a logic device on each Fx_Port. There are numerous waysto implement such logic devices, such as Application Specific IntegratedCircuits (ASICs), Field Programmable Gate Arrays (FPGAs), ErasableProgrammable Read-Only Memory (EPROMs), microprocessors ormicrocontrollers, or Digital Signal Processors (DSPs), includingsoftware executing on any of the foregoing. A preferred embodiment usesan ASIC as the logic device. Each ASIC contains fabric zoningconfiguration information in the form of a table providing a matrix ofsource and destination devices. Each potential source device and eachdestination device connected to the port would be contained in thematrix. This matrix is implemented as a bitmap, with a bit to be set orcleared in each position. Permitted source/destination devicecombinations would have their representative matrix bit set in thebitmap. Each port would contain such a bitmap.

Assume configuration 150 is in effect. As an example, the bitmap forF_Port 432 would contains bits which correspond to each of the otherFx_Ports 422, 442, and 452. The bits for F_Ports 422 and 442 wouldindicate that F_Port 432 is not permitted to receive communications fromthese ports; whereas the bit for FL_Port 452 would indicate that F_Port432 is permitted to receive communications from this port. Each of theASICs for the other Fx_Ports would contain analogous information. When amessage was received by F_Port 432, the zone check would be implementedby referencing the bitmap.

In another embodiment of the method of zone checking illustrated in FIG.6, the zone check may be performed on the devices themselves as opposedto the fabric. A logic device for performing this zone check could beinstalled on each device attached to the fabric system. Such a zonecheck could be performed by either the device sending the message or bythe receiving device.

In a preferred embodiment, the basic management of zones andconfigurations is accomplished in part by a fabric system administratorwho logs into a switch on the fabric and inputs zoning commands using asoftware interface. The administrator may use any switch in the fabricfor this purpose because a change made to the zoning information on oneswitch is propagated throughout all switches in the fabric. Other typesof management will be apparent to one of skill in the art. For example,the administrator may work from a dedicated device (e.g., a serverdedicated to managing the fabric and/or zoning) rather than through theindividual switches, or management functions may be performedautomatically by the fabric in response to commands from other computersrather than in response to inputs from a system administrator.

In a preferred embodiment of the invention, zoning management is brokendown into the following basic tasks: defining zones, defining zoneconfigurations, and selecting which configuration in a set is to be ineffect at any given time. To a certain extent, the software used toimplement zoning is flexible in regard to the order in which these stepsare performed. For example, it is possible to define a configurationthat refers to specific zones that have not yet been defined. The zonesmay then be defined at a later time, although it is preferable to definethe zones before the configuration containing the zones is put intoeffect. The following paragraphs describe preferred embodiments of eachof the basic tasks; other embodiments will be apparent.

Zones preferably are defined by identifying the devices which aremembers of that zone. Devices are typically identified by PhysicalFabric port number, Arbitrated Loop Physical Address (AL-PA), NodeWorldwide Name (Node WWN), or Port Worldwide Name (Port WWN). PhysicalFabric port numbers are specified as a pair of decimal numbers “s,p”where “s” is the switch number (domain ID from 0 to 31) and “p” is theport number on that switch (0 to 15). For example, “2,12” specifies port12 on switch number 2. When a zone member is specified by physicalfabric port number, then any and all devices connected to that port arein the zone. If this port is an arbitrated loop, then all devices on theloop are in the zone. AL_PA addresses are 8-bit addresses used byprivate loop devices that operate in a fibre channel Private Loop DirectAttach (FC-PLDA) environment. AL_PA is discussed in greater detail infibre channel 2^(nd) Generation Arbitrated Loop (FC-AL-2), revision 6.4(Project 1133-D), which is incorporated by reference in its entiretyherein.

A Worldwide Name uniquely identifies a fibre channel node or port on adevice. Worldwide Names are specified as eight hex numbers separated bycolons, for example “10:00:00:60:69:00:00:8a. When a zone member isspecified by Node Worldwide Name then all ports on that device are inthe zone. When a zone member is specified by Port Worldwide Name thenonly that single device port is in the zone. Specifying zone members byWorldwide Name is advantageous because, for example, a device which isso specified may be coupled to the fabric at any point or via any fabricelement and it will retain the same zone membership.

The type of zone members used to define a zone may be mixed and matched.For example, a zone defined with the following members: “2,12; 2,14;10:00:00:60:69:00:00:8a” would contain whichever devices are connectedto switch 2, ports 12 and 14, and the device with either the NodeWorldwide Name or Port Worldwide Name of “10:00:00:60:69:00:00:8a”.Alternatively, a fabric system administrator may assign an alias to azone to simplify repetitive entry of port numbers, AL_PAs or WorldwideNames. For example, the name “host” could be used as an alias for“10:00:00:60:69:00:00:8a”.

Zone configurations preferably are defined by specifying which zones aremembers of that configuration. For example, zone configuration 150 inFIG. 1 may be defined as “zone_140; zone_142” where zone_140 andzone_142 are zones defined as described in connection with FIG. 1. Whena zone configuration is in effect, all zones that are members of thatconfiguration are in effect. As with the definition of zones, commonnaming conventions, such as aliasing, may also be used with thedefinition of zone configurations.

More than one zone configuration may be defined for any given fabric.For example, in FIGS. 1 and 2, configurations 150 and 210 are twodifferent zone configurations which may be applied to fabric 110. Theset of all zone configurations which have been defined for a fabricshall be referred to as the “total defined configuration set.”

The actual configuration which is in effect shall be referred to as the“effective configuration.” Communications between devices are based onthe effective configuration. The effective configuration may be selectedby the fabric administrator or it may be programmed into the fabric. Forexample, in FIGS. 1 and 2, the fabric 110 may be programmed toautomatically implement configuration 210 every Saturday from 9-11 pm inorder to allow for regularly scheduled maintenance on loop 130 and toimplement configuration 150 at all other times.

A configuration is “compiled”, or reduced to a form usable by the fabric110, each time that it is put into effect. For example, configuration210 would be compiled every Saturday around 9 pm shortly before it isplaced into effect, and configuration 150 would likewise be compiledevery Saturday around 11 pm. The compilation procedure performs a numberof functions, such as checking for undefined zone names or otherinconsistencies, removing duplicate entries, resolving aliases, andconverting Worldwide Names to switch and port addresses if, for example,the fabric routes primarily based on switch and port addresses.

As part of the management function, configurations may also be saved. Ina preferred embodiment, saving will store a copy of the current “totaldefined configuration set” plus the name of the current “effectiveconfiguration” into a non-volatile storage medium, such as each switch'sflash memory. This “saved configuration set” is automatically reloadedby the fabric switches upon power up, including reinstating theeffective configuration from the saved configuration set. Note that thesaved configuration set may not reflect the most current total definedconfiguration set since changes may have been made since the last save.

The zoning commands described above are only one specific embodiment ofthe zoning management features of the present invention. Othermanagement functions; and/or combinations of commands will be apparent.For example, when an administrator is modifying the total definedconfiguration set, changes may be periodically auto-saved rather thanrequiring the administrator to affirmatively save any changes. Asanother example, any number of command sets and user interfaces may beused to implement the basic tasks described above.

Another aspect of zoning management concerns the handling of changes tothe fabric. For example, what happens to zoning when devices are addedto the fabric, or if multiple fabrics are merged into a single fabric.The switch or fabric to be added may either be new, meaning it has nopre-existing zoning information, or it may contain a previously definedset of zone configuration data. The following paragraphs describepreferred embodiments for handling these situations, although otherembodiments will be apparent.

If a new switch is added to a fabric, zoning information is copied fromthe fabric into the new switch. If a zone configuration is enabled inthe fabric, then the same configuration becomes enabled in the newswitch. Adding a new fabric (i.e., a fabric in which all the switcheshave no pre-existing zoning information) to an existing zoned fabric isvery similar to adding a new switch. Zoning information is copied fromthe existing zoned fabric into the switches of the new fabric. If a zoneconfiguration is enabled, then the same configuration becomes enabled inthe new fabric switches.

If two fabrics that both contain some existing zone configurationinformation are joined, then the situation is more complex. The zoningsoftware will attempt to merge the two sets of zone configuration datatogether, but this is only possible if the two sets of data arecompatible. The simplest case is where both fabrics have identical zoneconfiguration data and the same configuration is enabled. In this case,the fabrics are compatible and they will join to make one larger fabricwith the same zone configuration in effect across the whole new fabric.If the fabrics have different zone configuration data, then the two setsof zoning information will be checked for compatibility and merged ifpossible.

If a merge is not possible because the two zoning configuration datasets are incompatible, the fabric will be segmented. A merge is notpossible, for example, if the two zone configurations that are enabledare different, if different names are used by each fabric to refer tothe same zone, or if a zone with the same name in each fabric containsdifferent groups of devices in each fabric. If the merge is notpossible, then the fabric is logically segmented into two separatefabrics even though physically is it connected as a single fabric. Eachof the two new fabrics retains its original zone configuration.

Zones may also be configured to allow access between devices for onlycertain types of communication. For example, a zone may be configured topermit read-only access between devices, as opposed to the defaultread-write access generally permitted between devices within the samezone. Alternately, zones may also be configured as protocol zones, whichrestrict all devices within a zone to utilizing the same communicationsprotocol. Such zone types may be implemented in a number of ways. Forexample, referring to the previously described embodiment based on theSNS and additional zoning software, the zoning software may be modifiedto differentiate between zone types (e.g., normal, read-only, orprotocol) and the SNS may respond to a query for addresses by providinga list of other devices, including both address and type ofcommunication. Similar changes may be made to the other embodimentsdescribed above.

Although the invention has been described in considerable detail withreference to certain preferred embodiments, other embodiments arepossible. For example, zoning could be implemented via a centralized,versus distributed, method. In the previously described distributedmethod of implementing zoning, the zoning information is propagated toeach switch. However, this zoning information could also be containedand accessed in a centralized way, such as via a central zoning serverfor the entire fabric system. Therefore, the scope of the appendedclaims should not be limited to the description of the preferredembodiments contained herein.

What is claimed is:
 1. In a system comprising a first fabric and aplurality of devices coupled to the first fabric by Fibre Channelconnections, a method for logically organizing the devices comprising:accessing a definition of a first configuration including at least onezone, each zone including at least one device as a member of the zone;and responsive to the definition of the first configurations,restricting communications between the devices coupled to the firstfabric; wherein the step of restricting communications between thedevices includes, responsive to a first device querying for an addressof a second device, returning the address of the second device only ifthe first and second device are members of a common zone.
 2. The methodof claim 1 wherein the step of restricting communications between thedevices includes, responsive to a first device querying the first fabricfor a list of addresses of other devices coupled to the first fabric,returning a list of only the addresses of other devices which are in acommon zone with the first device.
 3. The method of claim 2 wherein thestep of restricting communications between the devices further includes,responsive to a change in the first configuration, signaling the firstdevice to requery the first fabric for a list of addresses of otherdevices coupled to the first fabric.
 4. In a system comprising a firstfabric and a plurality of devices coupled to the first fabric by FibreChannel connections, a method for logically organizing the devicescomprising: accessing a definition of a first configuration including atleast one zone, each zone including at least one device as a member ofthe zone; responsive to the definition of the first configuration,restricting communications between the devices coupled to the firstfabric; and responsive to a merging of the first fabric with a secondfabric, modifying the definition of the first configuration to accountfor the second fabric, wherein the step of modifying the definition ofthe first configuration includes: determining whether the definition ofthe first configuration is compatible with definitions forconfigurations for the second fabric; and responsive to a determinationof compatible configurations, propagating the first configuration to thesecond fabric.
 5. In a system comprising a first fabric and a pluralityof devices coupled to the first fabric by Fibre Channel connections, amethod for logically organizing the devices comprising: accessing adefinition of a first configuration including at least one zone, eachzone including at least one device as a member of the zone; responsiveto the definition of the first configuration, restricting communicationsbetween the devices coupled to the first fabric; and determining whetherthe definition of the first configuration is compatible with definitionsfor configurations for the second fabric; responsive to a determinationof compatible configurations, modifying the definition of the firstconfiguration to account for the second fabric and merging the firstfabric with the second fabric; and responsive to a determination ofincompatible configurations, segmenting the second fabric from the firstfabric.
 6. A fabric element for use in a system comprising a firstfabric and a plurality of devices coupled to the first fabric by FibreChannel connections, the fabric element comprising: a plurality ofports, each port adapted to be coupled to a device by a Fibre Channelconnection; a storage medium for storing a definition of a firstconfiguration including at least one zone, each zone including at leastone device as a member of the zone; and a logic device coupled to theplurality of ports and to the storage medium, for, responsive to thedefinition of the first configuration, restricting communications fordevices coupled to the plurality of ports, wherein the logic deviceincludes a name server for, responsive to a first device querying for anaddress of a second device, returning the address of the second deviceonly if the first and second device are members of a common zone.
 7. Acomputer readable medium containing software for logically organizing aplurality of devices coupled to a first fabric by Fibre Channelconnections, the software for instructing a processor to perform thesteps of: accessing a definition of a first configuration including atleast one zone, each zone including at least one device as a member ofthe zone; and responsive to the definition of the first configuration,restricting communications between the devices coupled to the firstfabric, wherein the step of restricting communications between thedevices includes, responsive to a first deice querying for an address ofa second device, returning the address of the second device only if thefirst and second device are members of a common zone.
 8. The computerreadable medium of claim 7 wherein the step of restrictingcommunications between the devices includes, responsive to a firstdevice querying the first fabric for a list of addresses of otherdevices coupled to the first fabric, returning a list of only theaddresses of other devices which are in a common zone with the firstdevice.
 9. The computer readable medium of claim 8 wherein the step ofrestricting communications between the devices further includes,responsive to a change in the first configuration, signaling the firstdevice to requery the first fabric for a list of addresses of otherdevices coupled to the first fabric.
 10. A computer readable mediumcontaining software for logically organizing a plurality of devicescoupled to a first fabric by Fibre Channel connections, the software forinstructing a processor to perform the steps of: accessing a definitionof a first configuration including at least one zone, each zoneincluding at least one device as a member of the zone; responsive to thedefinition of the first configuration, restricting communicationsbetween the devices coupled to the first fabric; and responsive to amerging of the first fabric with a second fabric, modifying thedefinition of the first configuration to account for the second fabric,wherein the step of modifying the definition of the first configurationincludes: determining whether the definition of the first configurationis compatible with definitions for configurations for the second fabric;and responsive to a determination of compatible configurations,propagating the first configuration to the second fabric.
 11. A computerreadable medium containing software for logically organizing a pluralityof devices coupled to a first fabric by Fibre Channel connections, thesoftware for instructing a processor to perform the steps of: accessinga definition of a first configuration including at least one zone, eachzone including at least one device as a member of the zone; responsiveto the definition of the first configuration, restricting communicationsbetween the devices coupled to the first fabric; and determining whetherthe definition of the first configuration is compatible with definitionsfor configurations for the second fabric; responsive to a determinationof compatible configurations, modifying the definition of the firstconfiguration to account for the second fabric and merging the firstfabric with the second fabric; and responsive to a determination ofincompatible configurations, segmenting the second fabric from the firstfabric.
 12. A Fibre Channel device for use in a Fibre Channel Fabric,the fabric coupling a plurality of external devices, the fabricconfigured into at least two zones, where the external devices areallowed to exchange data packets only with external devices in the samezone, an external device querying for address information when coupledto the fabric, the Fibre Channel device comprising: a Fibre Channel portfor receiving an address information query from an external device; astorage medium for storing a first configuration including at least twozones; a simple name server coupled to said Fibre Channel port and saidstorage medium for responding to the address information query withexternal devices address information only for external devices in thesame zone as the external device providing the address informationquery.
 13. A Fibre Channel switch for use in a Fibre Channel Fabric, thefabric coupling a plurality of external devices, the fabric configuredinto at least two zones, where the external devices are allowed toexchange data packets only with external devices in the same zone, anexternal device querying for address information when coupled to thefabric, the Fibre Channel switch comprising: a Fibre Channel port forreceiving an address information query from an external device; astorage medium for storing a first configuration including at least twozones; a simple name server coupled to said Fibre Channel port and saidstorage medium for responding to the address information query withexternal devices address information only for external devices in thesame zone as the external device providing the address informationquery.
 14. The Fibre Channel switch of claim 13, wherein said simplename server includes: a CPU module; and software executing on said CPUmodule to provide said simple name server functionality.
 15. A FibreChannel network comprising: a plurality of external Fibre Channeldevices; and a Fibre Channel fabric coupling said plurality of externalFibre Channel devices, wherein the fabric is configured into at leasttwo zones, where the external Fibre Channel devices are allowed toexchange data packets only with external Fibre Channel devices in thesame zone and the external Fibre Channel devices query for addressinformation when coupled to the fabric wherein said Fibre Channel fabricincludes: a Fibre Channel port for receiving an address informationquery from an external Fibre Channel device; a storage medium forstoring a first configuration including at least two zones; and a simplename server (SNS) coupled to said Fibre Channel port and said storagemedium for responding to the address information query with externalFibre Channel devices address information only for external FibreChannel devices in the same zone as the external Fibre Channel deviceproviding the address information query.